Victor H. Perez

Monoglicerídeos: produção por via enzimática e algumas aplicações

Monoglycerides (MAG) are non-ionic surfactants, widely used in the pharmaceutical, food and cosmetic industries. Although MAGs are manufactured on an industrial scale by chemical glycerolysis of oils and fats, new developments in lipase catalyzed synthesis have been studied as an alternative to the classical method seeking to use clean technology and green chemistry. In this work, different methods such as glycerolysis, selective hydrolysis of fats and oils, and esterification of fatty acids or transesterification of esters with glycerol are presented. The properties and applications of the monoglycerides are also included in this review.

Enzymatic synthesis of glyceride esters in solvent-free system: influence of the molar ratio, lipase source and functional activating agent of the support

This work assessed the influence of important factors that affect the synthesis of glyceride esters in solvent-free systems, such as: glycerol/fatty acid molar ratio, lipase source and activating agent of the support obtained by the sol-gel technique. Commercial lipase preparations were immobilized on polysiloxane-polyvinyl alcohol particles (POS-PVA) previously activated with different agents (glutaraldehyde, sodium metaperiodate and carbonyldiimidazole) and their performance on the esterification reaction was compared with commercial preparations of immobilized lipase (Lipozyme IM20, Novozym 435, Lipozyme RM IM and Lipozyme TL IM). The reaction medium containing excess glycerol favored the glyceride ester synthesis and the Lipozyme IM20 was found to be the most suitable immobilized lipase preparation, attaining molar conversions higher than 94%. The use of CAL B Lipase immobilized on POS-PVA also provided satisfactory performance (conversion of about 80%) and allowed the formation of 36% wt of 2,3-dihydroxypropyl dodecanoate (monolaurin).

Protease production using agroindustrial residues by thermophilic Bacillus sp in submerged fermentation: optimization of the culture medium using an experimental design approach

Thermophilic Bacillus sp. SMIA-2, produced protease when grown on apple pectic, whey protein and corn step liquor medium, whose concentration was varied from 3 to 10 gL-1, according to the central composite design 23. The experiments were conducted in shaker, at 50 °C, 150 rpm and initial pH 6.5. The results revealed that the culture medium affected both, cell growth and enzyme production. After graphical and numerical optimization procedure, the enzyme production reached its maximum value at 30 h fermentation, reaching, approximately, 70 U protein mg-1, suggesting that this process was partially associated to the growth.

Whitney Equisingularity, Euler Obstruction and Invariants of Map Germs from ℂn to ℂ3, n > 3

We study how to minimize the number of invariants that is sufficient for the Whitney equisingularity of a one parameter deformation of any finitely determined holomorphic germ f: (ℂn, 0) → (ℂ3, 0), with n > 3. Gaffney showed in [3] that the invariants for the Whitney equisingularity are the 0-stable invariants and the polar multiplicities of the stable types of the germ. First we describe all stable types which appear in these dimensions. Then we find relationships between the polar multiplicities of the stable types in the singular set and also in the discriminant. When n > 3, for any germ f there is an hypersurface in ℂn, which is of special interest, the closure of the inverse image of the discriminant by f, which possibly is with non isolated singularities. For this hypersurface we apply results of Gaffney and Gassler [6], and Gaffney and Massey [7], to show how the Le numbers control the polar invariants of the strata in this hypersurface. Gaffney shows that the number of invariants needed is 4n+10. In the corank one case we reduce this number to 2n+2. The polar multiplicities are also an interesting tool to compute the local Euler obstruction of a singular variety, see [12]. Here we apply this result to obtain explicit algebraic formulae to compute the local Euler obstruction of the stable types which appear in the singular set and also for the stable types which appear in the discriminant, of corank one map germs from ℂn to ℂ3 with n ≥ 3.